Through secretive negotiations with ISPs, the coalition has divided the internet into 'acceptable' and 'unacceptable' categories and cut people off from huge swathes of it at the stroke of a key.

David Cameron visits the offices of Netmums at CP House in Watford on February 14, 2012. Photograph: Getty Images.

There is no porn filter, and blocking Childline is not an accident

The idea of an internet porn filter has always been a political fiction, a conveniently inaccurate sound bite used to conjure images of hardcore fisting and anal rape in the feverishly overactive imaginations of middle Britain. What activists actually called for - and ISPs were forced to provide - is an 'objectionable content' filter, and there is a vast, damp and aching chasm between the two.

The language of the mythical 'porn filter' is so insidious, so pervasive, that even those of us opposed to it have been sucked into its slippery embrace. And so even when it turns out that O2 are blocking the Childline and Refuge websites, or that BT are blocking gay and lesbian content, we tend to regard them as collateral damage – accidental victims of a well-meaning (if misguided) attempt to protect out children from the evils of cock.

But this was never the case. As Wiredreported back in July, Cameron’s ambitions extended far beyond porn. Working through secretive negotiations with ISPs, the coalition has put in place a set of filters and restrictions as ambitious as anything this side of China, dividing the internet into 'acceptable' and 'unacceptable' categories, and cutting people off from huge swathes of it at the stroke of a key.

"As well as pornography, users may automatically be opted in to blocks on "violent material", "extremist related content", "anorexia and eating disorder websites" and "suicide related websites", "alcohol" and "smoking". But the list doesn't stop there. It even extends to blocking "web forums" and "esoteric material", whatever that is. "Web blocking circumvention tools" is also included, of course."

And the restrictions go further still. Over the weekend, people were appalled to discover that BT filters supported homophobia, with a category blocking, "sites where the main purpose is to provide information on subjects such as respect for a partner, abortion, gay and lesbian lifestyle, contraceptive, sexually transmitted diseases and pregnancy."

BT have since reworded this description to remove the 'gay and lesbian' reference, but given that their filtering is provided by an unnamed "third party supplier" it seems highly unlikely that the filter itself has changed overnight – merely the description. Such measures would never be taken against the 'heterosexual lifestyle' - this is discrimination, pure and simple, hard-coded into our national communications infrastructure.

Of course it’s impossible to see what’s been blocked other than through tedious trial and error. One website owner (@pseudomonas) asked BT on Twitter for information about whether their site was blocked, and their experience was something like talking to a brick wall who only speaks French. The bottom line here is that even parents have no idea what they’re actually blocking, and we have no way of assessing the harm caused by BT’s measures.

O2, the Slough-based BT spin-off, do allow people to check which websites are blocked, and although their filter has been around for a few years now, the results are terrifying. Their 'parental control' settings can be blocked from accessing Childline, Refuge, Stonewall or the Samaritans – which is even more frightening when you realise that they could just as easily be switched on by an abusive partner. The most vulnerable people in society are the most likely to be cut off from the help they need. As Adrian Short argues, some websites simply shouldn’t be blocked.

It was never really clear what the so-called porn filter was supposed to achieve; what problem it was trying to prevent. Filtering seems to have become a crutch for inept parents looking for an easy way to avoid having real conversations with their kids about sex, porn and the world outside their comfortable little cul-de-sacs. If their first sight of a vagina traumatizes your teenage child, then you have brought them up wrong - but of course the problem here is often the parent more than the child; the embarrassed mother of father – projecting their own feelings of discomfort and embarrassment around the topic of sex onto their child. There remains, despite a wave of public hysteria, no good evidence that porn has any detrimental effect on children.

What clearly does have an impact on children though is denying them sex education, suppressing their sexual identity, and shutting off access to child protection or mental health charities. In all this talk of porn filters, the rights of the children campaigners supposedly want to protect have been ignored or trampled. Children should have a right to good quality sex education, access to support hotlines and websites, and information about their sexuality.

We may not be able to stop bad parents cutting their children off from the world, but that doesn’t mean we should allow ISPs to build and sell the tools to do it with. What’s bewildering is that BT’s updated website now explicitly acknowledges that: "Parents should carefully consider the possible adverse effects from denying children of an appropriate age access to information on these issues." If your filter could cause adverse effects on children, then why are you still peddling it?

And that leads to perhaps the most important question of all here - why on Earth were these lists built in the first place? Who constructed a list of 'gay and lesbian' sites to ban? Who at BT commissioned it? On what grounds was this kind of institutional bigotry deemed acceptable? Is it still in effect, and if so, why? These were deliberate acts, which show that something very rotten has taken hold at the heart of the British Internet industry. We are entitled to far greater transparency and clearer answers than we’ve been getting so far.